Edge seal process and product

ABSTRACT

A liquid thermoset coating is described for application on and near surfaces of molded plastic parts where the resin rich phase has been disturbed or imperfectly formed. The coating has been found to be effective at minimizing paint pops and craters in subsequent finish coatings on said parts. Said paint pops and craters develop during heated cure cycles for the finish coatings. The coating which is applied to the heated part and subsequently cured is preferably an epoxy composition of low viscosity. The molded plastic parts are preferably fiber reinforced thermoset polyester parts with an in-mold coating to improve surface quality.

CROSS-REFERENCE

This is a divisional of application Ser. No. 08/081,744 filed Jun. 23,1993, pending of Robert W. Smith et al., for "Edge Seal Process andProduct."

FIELD OF INVENTION

The present invention relates to a method of reducing surface defectsknown as paint pops or paint craters by coating a plastic substratesurface, and more particularly coating a fiber-reinforced thermosetplastic substrate surface with a liquid thermoset coating composition toprovide a barrier to gases generated from the plastic during the bakingof subsequently applied surface coatings.

A preferred liquid thermoset coating is a liquid epoxy resincomposition. These coatings are applied to surfaces of the molded parts.The invention is particularly applicable where the resin rich skin ofthe part has been disturbed or was not completely formed. It is alsodesirable to apply the coating to a warm or hot part as this lowers theviscosity of the epoxy resin, allowing the epoxy to better penetrate thesurface of the plastic part.

BACKGROUND

Molded thermoset plastics are finding increased utilization assubstitutes for metals in a variety of areas such as automotive parts,recreational vehicles, etc. Many of these applications are for paintedparts requiring smooth surface appearance and these parts often havein-mold coatings to achieve the smoothness. These molded thermosets alsouse low profile additives to decrease part shrinkage during molding. Thelow profile additive and molding conditions can create internal porositythat can entrap air, gases, and volatile compounds. Any abrasion,cutting, or fracture of the molded parts creates disruptions of a resinrich skin on said molded part, said disruptions having enhanced surfaceporosity. It is known that during heated cure cycles for subsequentfinish paints (coatings) on fiber reinforced thermoset parts, blemishesin the top coating, known as paint pops or craters, can develop. It isbelieved that gases evolving from internal porosity are creating thesedefects as the gases try to escape from the molded part during theheated cure cycle for the coating.

U.S. Pat. No. 5,021,297 describes heating a molded plastic part(degassing the part) and then applying a thermoset powder coating overthe surfaces of the part that will be subsequently coated. To beeffective this barrier needs to be substantial, 1-6 mils thick.

SUMMARY OF THE INVENTION

In accordance with the present invention, a method of sealing any poroussurfaces created by abrasion, cutting, or fracture of a molded plasticsubstrate is provided. For the purpose of simplicity, these surfacescreated subsequent to molding will be referred to as machined surfacesto distinguish them from molded surfaces. The invention is alsoapplicable to resin rich molded surfaces which are discontinuous orincompletely formed. The method comprises preheating the substrate to atemperature above 120° F. (49° C.) and below the decompositiontemperature of the substrate; applying a liquid epoxy compositioncomprising one or more epoxy oligomers, a hardener for the epoxyoligomers, and optionally graphite and carbon black to said machinedsurfaces; and curing said coating composition. Optionally any excesscoating composition can be removed by processes such as wiping thesurface with a cloth prior to curing said coating composition. Theremoval of excess coating material may help force the coating materialinto cracks and pores, providing a better seal, and serves to level thesurface of the part minimizing subsequent sanding operations.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1, 2, and 3 show three different edges that may be created onmolded plastic parts. FIG. 1 is a part having a shear edge with flashing(B) which would be trimmed off by cutting or grinding. FIG. 2 shows athermoset part wherein the edge (C) has been cut to a particular angle.FIG. 3 shows a thermoset part wherein the edge (D) was groundperpendicular to the other surfaces. FIGS. 1 and 2 show an in-moldcoating (A) on said parts.

DETAILED DESCRIPTION OF THE INVENTION

Liquid thermoset coatings are described which are applied to anyuncoated surface of the part and preferably to machined surfaces ofmolded plastic parts. These coatings were found to minimize the numberof surface defects that occurred in subsequent surface coatings e.g.,paint on the same part during oven curing cycles for the subsequentlyapplied coatings. The defects to be minimized are known as paint pops orcraters in the cured coating. They are believed to be caused by gasestrapped below the coating traversing into and through the coating duringcuring. The liquid thermoset coatings of this invention are thought toprovide a barrier to the gases from the molded part that potentiallycause paint pops and craters.

Fiber-reinforced thermoset molded parts generally have internalporosity. Low profile additives in automotive type body panels mayincrease the tendency to create internal porosity while minimizing theshrinkage of the part's exterior dimensions. Most molded thermoset partshave a resin rich layer on the surface which was in contact with themold surface. This resin rich layer can partially block passage of gasesfrom the internal porosity to the surface. Any process which disruptsthis resin rich layer can increase the surface porosity of the parts.The name disrupted or machined surfaces will refer to any surface whichhas been altered by any processes such as cutting, abrasion, orfracture. These processes include die-cutting, deflashing, routing,sanding, punching out holes, and drilling. Solvent treatment andhandling of the part during manufacturing and transporting can alsocause disruption of the resin rich layer. They can be distinguishedeasily from molded surfaces. The term machined as used herein does notspecifically require that a machine be used to create the surface.

Surface defects in subsequent coatings caused by the escape of trappedgases are more prevalent on or near machined surfaces than more removedareas of the part. As these machined surfaces are created after in-moldcoating has occurred, these surfaces are not in-mold coated. The poresof the porous plastic can be from a size large enough to be visible tosubmicron sizes. The pores are believed to supply gases during heatedcure cycles that can pass through partially cured coatings creatingeither holes, craters or paint pops. It is preferred to apply thesecoatings only to machined surfaces (surfaces created subsequent tomolding) and/or surfaces where the resin rich layer has been disrupted,as the internal porosity of the parts is most open to the surface atthese points. Experience has shown that surfaces adjacent to themachined surfaces (for some unknown reason) exhibit an increasedtendency to generate surface defects. Accordingly it is expeditious toalso cover the adjacent surfaces with the liquid thermoset coating. Thecoating may also be applied to surfaces other than disrupted surfaceswhere surface defects are a problem.

The preferred porous plastic parts useful as substrates for the coatingare thermosets, with fiber reinforced thermosets being highly preferred.Examples of thermoset plastics are unsaturated polyester resins, epoxyresins, acrylic terminated epoxy resins (also known as vinyl esterresins), phenolics, and melamine formaldehydes. Unsaturated polyestersand vinyl ester resins are preferred. A preferred substrate is a fiberreinforced thermoset part having from about 10 to about 75 wt % glassfibers and preferably from about 25 to 35 wt % glass fibers. It is alsopreferred that these molded parts have in-mold coatings on one or moresurfaces of said parts. In-mold coatings are well known to the art. U.S.Pat. No. 5,084,353, is hereby fully incorporated by reference anddiscloses a preferred in-mold coating.

Various fibers and methods of fiber reinforcement are available toreinforce plastic parts. Fibers can be fiberglass (solid or hollow),nylon, carbon, aramid, etc. The fibers can be present as chopped,nonwoven webs, woven webs, bundles, strands, etc. The preferred fibersare chopped fiberglass bundles of from about 0.5 to about 1.5 inches(1.3 to 3.8 cm) in length. Fiber reinforced plastic parts can be madefrom compounds called sheet molding compound (SMC), bulk moldingcompound (BMC), thick molding compound (TMC), or by processes involvingprepregs, wet layup, wet wind systems, and filament winding. Any ofthese compounds or processes would be suitable to form the fiberreinforced plastic substrate parts of this invention.

The porous plastic can include various additives such as low profilecompounds, mold release agents, viscosity modifiers, and mineral fillerssuch as calcium carbonate, dolomite, clays, talcs, zinc borate, perlite,vermiculite, hollow or solid glass or polymeric microspheres, hydratedalumina, and the like.

The liquid thermoset coating is desirably a liquid at room temperatureand desirably has a Brookfield viscosity at 25° C. of about 4000 poiseor less and preferably about 2000 or 1000 poise or less such that it canbe easily applied to the disrupted surfaces as a liquid. Coatingcompositions with high concentrations of conductive pigments were foundto be pastelike at Brookfield viscosities of 700 poise at 10 rpm and100° F. Therefore, conductive edge sealer compositions desirably haveviscosities of 500 poise or less and more desirably of 300 poise or lessso they can easily wet and adhere to the surfaces of a molded part. Thecoating can be applied with any known method such as brush, roller,sponge, spatula, an air or airless sprayer or other conventional coatingapplicator. After a uniform coating is applied to the desired area ofthe plastic substrate, any excess coating material may be removed.Preferred methods of removal include wiping with a cloth, sponge,squeegee, or equivalent. Thus, the coating can be made or reduced to 5mils or less, preferably from about 0.5 to about 3 mils thick, and mostpreferably 1 mil or less thick.

Preferred liquid thermoset coatings are epoxy resins cured withpolyamide curing agents. Preferred epoxy resins are those derived fromthe reaction product of bisphenol A with epichlorohydrin. Thus, apreferred epoxy resin is the diglycidyl ether of bisphenol A as shownbelow: ##STR1## where n is an integer from 0 to 5 and is preferably O.An important criteria in selecting an epoxy resin is the viscosity.Desirably they have an epoxy equivalent weight from about 156 to 350.Lower molecular weight resins have lower viscosities. Other epoxy resinsinclude polyglycidyl ethers of polyphenols such as those made from alkylor halogen substituted bisphenol A, epoxies from bisphenol F, phenolformaldehyde resins reacted with epichlorohydrin (novolak epoxies),tetraphenylolethane epoxy; dicycloaliphatic epoxy resins made by theepoxidation of cycloolefins with peracids; aromatic glycidyl amineresins; polyglycidyl esters formed from aliphatic, cycloaliphatic, oraromatic polycarboxylic acids which are reacted with epichlorohydrin andthen dehydrohalogenated; polyglycidyl ethers of polyhydric polyols; andcycloaliphatic epoxy resins. These desirably have 2 or more reactive1,2-epoxy groups per molecule or oligomer. The term epoxy resinsincludes blends of the above epoxy resins. It is anticipated that onewould blend epoxy oligomers to help control the viscosity of the finalepoxy composition.

Epoxy diluents may be included in the epoxy composition either in theepoxy resin as purchased or purposefully added to lower the viscosity ofthe epoxy composition. Epoxy diluents as defined here are similar to theabove-type chemical compounds, useful to make epoxy resins having1,2-epoxy groups, but are modified or reacted in such a manner toproduce an average of from about 1 to less than 2 1,2-epoxy groups permolecule. These are preferred to non-reactive diluents in that they arecapable of being chemically bound into the epoxy network and thus arenot easily volatilized. Another desirable characteristic of the epoxydiluents is that they have a lower viscosity than the above epoxyresins. Desirably these viscosities are less than 15 poise, desirablyless than 10 poise, or and preferably less than 5 poise, as measured bya Brookfield viscometer at 100° F.

The hardener composition can consist of curing agents that react withthe epoxy to form a crosslinked network or a catalyst that increases thespeed of the epoxy polymerization reaction or allows the reaction tooccur at a lower temperature. The catalysts include tertiary amines andLewis acids. The catalysts may be present up to about 10 parts by weightper 100 parts by weight of said thermoset coating and is desirablypresent from about 0.5 to 8 parts by weight. The curing agents may bepresent in small or large amounts depending on heir equivalent weight.Desirably, the equivalent ratio of reaction sites on the curing agent toepoxy groups is from about 0.3 to 3, and preferably from about 0.4 to 1.

The curing agent may be a amidopolyamine such as fatty acidpolyethyleneamine based polyamide; a polyamine such as diethylenetriamine, triethylene tetramine or higher homologues; a latent curingsystem such as a mixture of Ancamine™ 2014 FG and dicyandiamide; orcyclic acid anhydrides such as phthalic anhydride, hexahydrophthalicanhydride, maleic anhydride, itaconic anhydride, acetylcitric anhydride,aconitic anhydride and trimellitic anhydride. Other curing agents thatmay be employed include substituted imidazoles (e.g.,2-ethyl-4-methylimidazole), hydrazides (e.g., carbohydrazide),aminothiols, polythioureas and phenols, including phenolformaldehydenovolac resins. Catalysts can include a Lewis base such asbenzyldimethylamine, benzyldiethylamine, triethylamine, pyridine,tripropylamine, tributylamine, 2-picoline, and 4-picoline. Lewis acidssuch as boron trifluoride or aluminum chloride can also be used.

The liquid thermoset coating may contain a variety of additives toenhance certain aspects of its performance. Conductive pigments such asgraphite and carbon black can be added to make the coating conductive.Desirably, these two pigments are used in combination. The graphite candesirably be present up to about 150, more desirably from about 5 toabout 120, and preferably from about 20 to about 75 parts per 100 partsof said epoxy composition. The carbon black is desirably present up toabout 25, more desirably from 0.5 to about 15, and preferably from about1 to about 10 parts by weight per 100 parts of said epoxy composition.Lower viscosity epoxy resins or epoxy diluents may be used to minimizeviscosity increases associated with the use of these conductivepigments.

Other possible additives are pigments, fillers, adhesion promoters, andprotectorants, such as UV absorbers, from environmental factors.Desirably, the amount of non-reactive (inert) diluents (solvents) areminimized. The term non-reactive is used here to mean that thesemolecules do not chemically react into a thermoset polymer network withthe other molecules during the curing reaction of the liquid thermosetcoating. Thus, they are free to evaporate before, during, or after thecuring reaction. The amount of these diluents is desirably limited toless than 30, more desirably less than 10, and preferably not presentabove 5 parts by weight per 100 parts by weight of the liquid thermosetcoating. Most preferably, the liquid thermoset coating is substantiallyfree of non-reactive diluents.

It is desirable to preheat the substrate to a temperature from about120° F. (49° C.) to about 400° F. (204° C.), more desirably from about170° F. (77° C.) or 200° F. (93° C.) to about 350° F. (177° C.) , andpreferably from about 250° F. (121° C.) to about 300° F. (149° C.)before applying the coating. This may serve to minimize the amount ofvolatiles or gases in the porous part before coating. It also thins thecoating material and lowers the surface energy of the epoxy resinallowing it to better penetrate the surface of the part. Then thecoating is cured at an appropriate temperature. Desirably, the coatingis cured within a few minutes or hours after being applied. The curingtemperature depends on the curing mechanism. For epoxy resins, thecuring temperature is desirably from about 25° C. to about 200° C.,preferably from about 40° C. to about 175° C., and most preferably fromabout 100° C. to about 160° C.

The machined surfaces of the plastic part are coated with the liquidthermoset coating and cured. Then the part may be coated with one ormore coatings (paint) and said one or more coatings cured individuallyor jointly at elevated temperatures such as from 200° F. (93° C.) to400° F. (204° C.). The coatings will have a decreased propensity to havecoating defects in the form of holes, craters, or paint pops in or nearthe machined areas sealed when the edge sealant is present.

The liquid thermoset coating and the substrate with this cured coatinghave particularly effective utility as an edge seal on machined in-moldcoated thermoset BMC, SMC, and TMC parts. The edge seal has utility onsurfaces where the in-mold coating was not applied or where it wasabraded away, ruptured, or removed. As previously mentioned, the coatingmay be utilized on surfaces where the resin rich layer is discontinuousor incompletely formed. Common causes of discontinuities are airentrainment, insufficient dispersion of fillers or fibers, microcracksfrom localized failure and non-compacted resin areas. Names for thediscontinuities include pits, pores, cracks, and crevices. The uses forthese parts include automobile body panels, parts on recreationvehicles, and housings for electronics. The liquid thermoset coating canalso function as a sealant for a variety of parts made from orientedfibers by processes where prepregs, wet resin layup, wet wind systems,and filament winding are used. These parts can also serve as structuralcomponents.

In these applications, the thermoset molded parts with their machinedareas sealed can be subsequently coated and thermally cured with fewerrejects and less need for reworking of defective paint finishes.

EXAMPLES

An SMC paste was prepared by mixing an unsaturated polyester resin asshown in Table I below. The low profile additive was poly(vinylacetate), the inhibitor was hydroquinone, the catalyst was t-butylperbenzoate, and the mold release was zinc stearate. The unsaturatedpolyester was a poly(propylene fumarate) copolymer having an averagemolecular weight of between 1000 and 1600 with trace amounts of diolsother than propylene diol.

                  TABLE I                                                         ______________________________________                                        Paste                                                                         ______________________________________                                        Unsaturated Polyester                                                                            13.8%,   by weight                                         Low Profile Additive                                                                             9.2%                                                       Styrene            3.7%                                                       Inhibitor          0.005%                                                     Peroxide Catalyst  0.25%                                                      Viscosity Reducer  0.8%                                                       Mold Release       1.0%                                                       Calcium Carbonate  69.8%                                                      MgO                1.4%                                                       TOTAL:             100.                                                       ______________________________________                                         Fiber Glass: 1 inch long chopped strand fiberglass.                           Final SMC Composition: 20 parts by wt. fiberglass based on 80 parts by wt     paste.                                                                   

The SMC was compression molded in a 16"×16" mold for 90 seconds at 300°F. (149° C.) using centrally placed square charges of SMC that coveredeither 47% (10×10") or 66% (13×13") of the mold surface and gave 0.1"thick moldings. The higher mold coverage charge gave molded panels withmore internal porosity and subsequently a greater tendency to have paintpops. The top surface of the panels and all four sides were first sandedwith a 220 grit sandpaper and then a 320 grit sandpaper to open thisinternal porosity to the surface. The panels were then heated for 1/2hour at 320° F. (160° C.). Liquid thermoset coatings 1, 2, and 4-11 ofTable II were applied to the hot parts while coatings 3, 12, and 13 wereapplied to cold parts. The various compositions were applied to 1/2 thetop surface of the panels and to 1/2 of the edges. The other half ofeach panel was not coated and was used as an uncoated control. Eachcoating was tried on 6 panels. The coatings were allowed to briefly soakand then the excess was removed by wiping with a clean cellulosic cloth.The coating and panel were then put in a 320° F. (149° C.) oven for 1/2hour. The panels were then alternately painted with one of two paintsystems.

The A coating system was primer from Seibert Oxidermo (high solidsconductive primer) having code #BP9471 which was baked 30 minutes at300° F. and 30 minutes at 400° F. Then a BASF primer code #U280RK035 wasapplied and baked for 30 minutes at 300° F. Then a PPG White enamel code#ESBM33T100 was applied and baked for 30 minutes at 275° F. Thesecoatings were applied to all surfaces of the part (both sealed andunsealed).

The B coating system was a PPG code #RPP9860 light gray primer (apolyester melamine type coating) which was baked on for 20 minutes at250° F. Then a DuPont white topcoat code #872-DF167 (apolyester-acrylic-melamine coating) was applied and allowed to flash for5 minutes over which was applied a DuPont code #RK-7103 clear coat (anacrylic melamine coating). The application of the clear coat was a weton wet coating type. The clear coat was allowed to flash for 10 minutesbefore baking. Then the last two coatings were simultaneously baked for30 minutes at 250° F.

Three panels with the A coating and three with the B coating wereexamined. The number of holes and craters were then counted on thesealed and unsealed flat portions of the panels. The results are shownin Table II. A hole is a circular depression in the paint with a raisedrim around its periphery. It is about 1 mm across, and has a small holeat its center that leads to the substrate through the paint layers. A"crater" is a smooth irregular shaped hole in the paint ranging in sizefrom 0.1 mm to 1 or 2 mm. Most are caused by shallow pits in thesubstrate.

                                      TABLE II                                    __________________________________________________________________________    Coating              Unsealed    Sealed                                       Composition   Finish Paint                                                                         Craters                                                                           Holes                                                                             Total                                                                             Craters                                                                           Holes                                                                             Total                                __________________________________________________________________________      Epon 815.sup.1 + V-40.sup.2 +                                                             A      2   3    5  2   10  12                                     Graphite + Carbon                                                             75:25:32:1.6 by wt.                                                                       B      18  18  36  0   5   5                                      Epon 828.sup.3 + V-40 +                                                                   A      11  12  23  0   1   1                                      Graphite + Carbon +                                                           Epoxy Diluent                                                                 65:25:32:1.6:10                                                                           B      28   9  37  3   1   4                                      Derakane 786.sup.4 + Sty-                                                                 A      3   18  21  0   21  21                                     ene + 1 wt. % TBP                                                             70:30:1 by wt.                                                                            B      7    6  13  5   11  16                                     Epon 828 + V-40                                                                           A      16  18  34  0   5   5                                      3:1 by wt.  B      11  30  41  1   19  20                                     Epon 828 + V-40 +                                                                         A      2   13  15  0   3   3                                      Xylene                                                                        3:1:1 by wt.                                                                              B      20  25  45  3   3   6                                      Epon 828 + Dyhard.sup.5 +                                                                 A      5    7  12  0   2   2                                      Ancamine 2014.sup.6                                                           100:5:6     B      7   16  23  5   1   6                                    7 Gluvit.sup.7 + Hardener                                                                   A      3    7  10  1   4   5                                      7.5:1 by wt.                                                                              B      16  13  29  1   3   4                                      Epon 825 + V-40 V-50.sup.2                                                                A      0    0   0  0   5   5                                      4:3 by wt.  B      16   2  18  0   2   2                                      Epon 830.sup.8 + V-25.sup.9                                                               A      9   12  21  0   0   0                                      10:9 by wt. B      4    6  10  0   0   0                                    10.                                                                             Epon 828 + V-40 +di                                                                       A      2    5   7  0   8   8                                      butyl phthalate                                                               3:1:1       B      6   10  16  0   5   5                                      Derakane 684-EK.sup.10 40 +                                                               A      2   11  13  2   10  12                                     Toluene                                                                       1:1 by wt.  B      23   8  31  60  7   67                                     Shellac based primer                                                                      A      1   19  20  0   16  16                                     Sealer      B      24  18  42  16  12  28                                     Ed-Tech.sup.11 + hardener                                                                 A      3    6   9  2   15  17                                     50:1 by wt. + styrene                                                                     B      12  13  25  19  3   22                                   __________________________________________________________________________     .sup.1 Epon 815 is liquid epoxy resin similar to Epon 828 with a reactive     diluent.                                                                      .sup.2 V40 and V50 are polyamide curing agents.                               .sup.3 Epon 828 is bisphenol A based epoxy resin.                             .sup.4 Derakane 786 is vinyl ester resin.                                     .sup.5 Dyhard is a hardener for epoxy resin.                                  .sup.6 Ancamine 2014 is a hardener for epoxy resins.                          .sup.7 Gluvit is a commercial epoxy marine repair kit available from          Travaco Labs, Inc.                                                            .sup.8 Epon 830 is liquid epoxy resin.                                        .sup.9 V25 is polyamide from MillerStephenson                                 .sup.10 Derakane 684EK40 is a Dow onecomponent epoxy product.                 .sup.11 EdTech is an unsaturated polyester.                                   TBP is tertiary butyl perbenzoate                                        

The above data show that the Derakane resins (unsaturated polyesterresins) are not as effective as the epoxy resin. The epoxy resins weregenerally effective. The Ed-Tech material, which is a commercialpolyester patching compound, was also not effective. The shellac wasalso found to be less effective at preventing paint pops. Coating 10used a less volatile diluent while coating 11 used a volatile diluent.

In later experiments the epoxy compositions were diluted with solventsto adjust their viscosity. These diluted compositions were not aseffective at minimizing paint defects as were the undiluted compositionsapplied to hot substrates, but they still show improvement in reducingsome types of defects such as crater reductions with composition 10.

In that many plastic parts have a conductive in-mold coating and aresubsequently coated electrostatically, it was desirable that the edgeseal be conductive. The following formulations in Table III show thatwhen a conductive carbon black pigment (Vulcan XC-72R from Cabot Corp.),was added to a coating composition, it did not give good adhesion.Unexpectedly, the addition of graphite (traditionally thought of as alubricant not an adhesive agent) increased the adhesion of coating tothe substrate. The use of graphite alone (when used at 32 g/100 g oftotal epoxy resins) did not show sufficient conductivity. Thecombination of graphite and carbon black gave a conductive coating withgood adhesion. The substrate was a 16"×16" fiberglass panel similar tothe SMC composition in Table I, and cured for about 90 seconds at 300°F. (149° C.). The coating material was applied as a 2 or 3 mil thickcoating to one side of the panels with a spatula and cured for 20minutes at 300° F. (149° C.) before being evaluated.

                  TABLE III                                                       ______________________________________                                                      Formulation                                                                   A        B       C                                              ______________________________________                                        Part A                                                                        Epon 828 Resin  .sup. 65.0 g                                                                             65.0    65.0                                       Cardolite NC-513.sup.1                                                                        10.0       10.0    10.0                                       #508 Graphite Powder.sup.2                                                                    --         24.0    24.0                                       Vulcan XC-72R.sup.3                                                                           2.5        --      1.2                                        Part B                                                                        Epon Hardener V-40                                                                            25.0       25.0    25.0                                       #508 Graphite Powder                                                                          --         8.0     8.0                                        Vulcan ™ XC-72R                                                                            0.5        0.4     0.4                                        Conductivity (Ransberg                                                                        135        0       135                                        Meter Reading).sup.4                                                          Adhesion (scalpel, a                                                                          Poor       Good    Good                                       severe test)                                                                  ______________________________________                                         ##STR2##                                                                      available from Cardolite Corp., in Newark, New Jersey (USA).                  .sup.2 #508 Graphite powder was supplied by Ashbury Graphite Mills is 85      wt. % or more carbon and passes through a 325 mesh screen.                    .sup.3 Vulcan ™ XC72R is a high structure carbon black available from      Cabot Corp.                                                                   .sup.4 Conductivity was tested with a Ransberg meter available from           Ransberg ElectroCoating Corporation. Values above 120 are suitable for        electrostatic painting.                                                  

In the above examples of Table III, a reactive epoxy diluent, CardoliteNC-513 was used to reduce the viscosity of the epoxy composition. TableIV shows the reduced viscosity of recipes I and II over the controlwhich lacks low viscosity epoxy reactants. All parts in Table IV are byweight.

                  TABLE IV                                                        ______________________________________                                        COMPONENT A                                                                   INGREDIENTS     CONTROL    I        II                                        ______________________________________                                        Epon 828        75.0       75.0     75.0                                      #508 Graphite   24.0       24.0     24.0                                      Vulcan XC-72R   1.2        1.2      1.2                                       Tetraethylammonium                                                                            0.5        0.5      0.5                                       Tosylate                                                                      Cardolite NC-513                                                                              --         10.0     --                                        Union Carbide UVR-6110.sup.1                                                                  --         --       10.0                                      BROOKFIELD                                                                    VISCOSITY, cps                                                                (Model DV II, Spindle D)                                                                      70,400     24,000   49,600                                    10 rpm                                                                        (100° F.) 100 rpm                                                                      47,500     13,600   29,400                                    ______________________________________                                        COMPONENT B                                                                          INGREDIENTS                                                                             I                                                            ______________________________________                                               V-40 Hardener                                                                           25.0                                                                #508      8.0                                                                 Vulcan XC-72R                                                                           0.4                                                          ______________________________________                                        FINAL COATINGS (3:1 A:B BY WT.)                                               COATING         CONTROL     I        II                                       ______________________________________                                        Brookfield Viscosity, cps                                                     (Model DV II, Spindle D)                                                                      Not Measured                                                                              8,000    17,600                                   10 rpm                                                                        (100° F.) 100 rpm                                                                      Not Measured                                                                              4,800     7,040                                   ______________________________________                                         Coatings I and II were applied to sanded SMC panels, and cured at             300° F. for 10 and 20 minutes, as noted. The coating properties        were as follows:                                                         

    COATING  PENCIL                                                               (CURE    HARD-     GRAVEL-   CROSS-  CONDUC-                                  TIME)    NESS      OMETER.sup.2                                                                            HATCH.sup.3                                                                           TIVITY                                   ______________________________________                                          I (10 min.)                                                                          H/HB      9         1       130                                        I (20 Min.)                                                                          H/HB      8         0       136                                      II (10 min.)                                                                           H/HB      8         0       135                                      II (20 min.)                                                                           H/HB      7         0       136                                      ______________________________________                                         .sup.1 Union Carbide UVR6110 is                                               ##STR3##                                                                      which has a viscosity of 350-450 cp by Brookfield viscometer at 25.degree     C.                                                                            .sup.2 Gravelometer test is SAE J400 and more specifically GM 9508P.          .sup.3 Crosshatch Tape Adhesion is Ford Laboratory Test (FLTM) BI 61.    

While in accordance with the Patent Statutes, the best mode andpreferred embodiment has been set forth, the scope of the invention isnot limited thereto, but rather by the scope of the attached claims.

What is claimed is:
 1. A laminate comprising:a molded thermoset plasticpart having at least one machined surface and at least a first coatingand a second coating, said first coating being a coating to improve thesurface quality of the molded part, said second coating being a reactionproduct comprising a liquid epoxy resin composition, said epoxy resincomposition comprising an epoxy terminated oligomer having at least tworeactive epoxy groups and a hardener component reactive with said epoxygroups, said liquid epoxy resin composition having a Brookfieldviscosity at 25° C. of less than about 4000 poise, said second coatingbeing present on the at least one machined surface of the molded part.2. A laminate according to claim 1, wherein said first coating is anin-mold coating.
 3. A laminate according to claim 1, wherein said firstcoating is a primer layer.
 4. A laminate according to claim 2, includingat least one additional coating, wherein one of said at least oneadditional coating is a primer layer.
 5. A laminate according to claim2, wherein said epoxy resin having at least two reactive epoxy groups isat least 50 wt. % diglycidyl ethers of bisphenol A having epoxyequivalent weights from about 156 to about
 350. 6. A laminate accordingto claim 2, wherein said molded plastic part is a fiber reinforcedthermoset polyester or thermoset vinyl ester resin part.
 7. A laminateaccording to claim 6, wherein said epoxy resin having at least tworeactive epoxy groups is at least 50 wt. % diglycidyl ethers ofbisphenol A having epoxy equivalent weights from about 156 to about 350.8. A laminate according to claim 6, where said second coating includesconductive pigments and optionally a reactive epoxy diluent that hasfrom about 1 to less than 2 epoxy groups per molecule.
 9. A laminateaccording to claim 2, wherein the laminate further comprises at leastone subsequent coating which is cured at a temperature from 93° C. to204° C.
 10. A laminate comprising:a molded thermoset plastic part havingat least one machined surface and at least a first and a second coating,said first coating being a reaction product comprising a liquid epoxyresin composition of at least an epoxy terminated oligomer having atleast two reactive epoxy groups and a hardener component reactive withsaid epoxy groups, said liquid epoxy resin composition having aBrookfield viscosity at 25° C. of less than 4000 poise, and said secondcoating being one or more coatings applied over said first coating andsaid second coating being cured at temperatures from about 93° C. toabout 204° C., said first coating being present on the at least onemachined surface of said part and being cured prior to the applicationof the second coating.
 11. A laminate comprising:a molded thermosetplastic part having least one machined surface and at least a firstcoating, said first coating being a reaction product comprising at aliquid epoxy resin composition of at least an epoxy terminated oligomerhaving at least two reactive epoxy groups and a hardener componentreactive with said epoxy groups, said liquid epoxy resin compositionhaving a Brookfield viscosity at 25° C. of less than 4000 poise whereinsaid first coating is present on said at least one machined surface andareas immediately adjacent thereto.
 12. A laminate comprising:a moldedplastic part having at least one coating thereon, wherein one of said atleast one coating is a reaction product comprising a liquid epoxy resincomposition of at least an epoxy terminated oligomer having at least tworeactive epoxy groups and a hardener component reactive with said epoxygroups, said liquid epoxy resin composition having a Brookfieldviscosity at 25° C. of less than 4000 poise.